In what ratio should water and wine be mixed so that after selling the mixture at cost price a profit of 20% is made?
The water will be sold at the price of wine. So the profit will be earned by selling water as wine. Profit% = $\text"Profit"/\text"Cost"$ × 100. If profit percent is 20%, then 1 part of pure water is sold at the cost of 5 parts of wine. So the required mixing ratio should be 1 : 5.